# Small Wind Payback

L. David Roper
http://www.roperld.com/personal/roperldavid.htm
6 April, 2016

## Introduction

Wind energy is an inflation-protected investment; it reduces electricity costs at the current rate instead of future rates. The economics of wind energy include:

The first thing you should do is make your house as energy-efficient as possible, so that renewable energy does not have to supply so much energy.

## Assumptions

Several assumptions have to be made to calculate payback for small wind energy; here is an example:

• Initial electricity rate: ~\$0.10/kWh for Blacksburg VA
• Average yearly increase in grid-electricity rate: ~6%/year
• Cost per peak kilowatt to install: ~\$4000/(peak kW)
• Loan interest rate: ~5% per annum
• Actual turbine output per year: ~30% (Depends on the yearly average wind.)

There are some ephemeral situations that may reduce payback periods:

• State or federal rebates for installing renewable energy
• State or federal tax deductions or reductions for installing renewable energy
• Solar Renewable Energy Credits (SRECs) that may be saleable

In the spreadsheet described below there are two worksheets; one for true cost and one for including ephemeral reductions.

## Wind Study

To find out if there is enough wind at the chosen site, a wind study must be done. Here is a procedure to follow:

1. Find out what is the maximum height allowed for a wind turbine at the site.
2. Put an anemometer at the top of a pole at the allowed height and record the wind for a year to get the yearly average wind speed. (An average of more than 5 m/sec is needed.) (Some states have anemometer loan programs; check on the Internet. E.g., Ohio.)

References for anemometers:

## Green Investment

A Home Power Magazine study showed that, with reasonable assumptions, investing in green infrastructure for your home and business can return as much or more money savings as investing in the stock market earned over the last twenty years. And if enough information were available to calculate the money saved by not dumping carbon into the atmosphere, the energy-efficient investment would be even more favorable. This is a good time for U.S. citizens to buy products from companies to make their homes and businesses more energy efficient instead of buying stock in companies, which may go into increasing the salaries of executives. Make companies earn the money they receive from you by actually creating products you need for energy efficiency

## Energy Payback and Carbon-Emissions Payback

As important as money payback are energy payback and carbon-emissions payback for solar PV systems. Some good references for these calculations are:

All of these calculations agree that the energy payback and carbon-emissions payback are 1-10 years.

## References

L. David Roper, http://www.roperld.com/personal/roperldavid.htm
6 April, 2016